Repair Topics / Engine Over Heating-1 / Engine Over Heating-2 / Engine Over Heating-3 / Engine Over Heating-4

• Why does my engine over heat or run hot?
• Why is my engine leaking coolant?
• How to change your radiator
• Why is there oil in the coolant?
• Why is there coolant in the engine oil?
• Why does my engine leak oil?
• Why is my heater not working?
• Why is my engine making noise?
• How a cooling system works
• How to test a thermostat
• How does a clutch fan work?
• How does a serpentine belt tensioner work?
• Car is making a bubbling noise
• Why is my car making a popping noise?

MORE: Car over heating questions

Car Engine Over Heating Condition and Coolant Loss - This category contains featured questions as examples. They relate to most vehicles.

Answer: When the engine is running hot and the radiator fan should be on, check for 12 volts to the fan.  If there is no voltage, there is a relay or sensor that has failed.  If there is voltage, then the fan motor needs replacing.

Question: 1995 Chevrolet Corvette lt1 350cid_mileage: 116,00. I am having a problem with my cooling system on my 95 vette. Here is what it's doing. I bought it in June about a week after I had it I got a low coolant light. I filled the high pressure tank like it says in owners manual. It will blow the coolant out only when I stop the engine. I have replaced the cap has new high performance aluminum radiator which I installed. I elevated the front end as said in radiator instructions also a Chevy mechanic at the dealer said to elevate the front to get all the air out of system. I am still having it blow the coolant out I also replaced thermostat. Engine temp is running 188-191 on highway in town 205 at most. But when I stop and shut the engine off you can here what appears to be air bubbles and that’s when it starts blowing the coolant into the overflow tank.

Answer: Perform a cylinder leak-down test on the engine which will show if you have a blown head-gasket and/or cracked cylinder head.

Question:  2001 Lincoln Town Car mileage: 85,000. At about 75,000 miles, 70 mph, outside temperature at 95 deg the car overheats, and the A/C cuts out. Wait awhile, leave A/C off and car stays hot but doesn't overheat. Cooling fan motor changed, thermostat changed twice, cooling system flushed twice and pressure tested twice. This condition only happens at high speeds and hot outside temperatures.

Answer:  Check for blockage in the radiator.  Flushing the cooling system will not fix a partially plugged radiator.  Replace radiator with new to repair problem.

Question: 2001 Dodge Neon mileage: 111,000. I replaced my head gasket 3 times all ready and this last time I installed a new cylinder head. At 37,000 miles, I started having overheating problems. I live in Phoenix, AZ and the temperature is 110 degrees every day. I found out my car overheats when the temperature is over 98 degrees outside. I replaced the cylinder head, radiator cap, new radiator, all hoses, temperature sensor, position sensor, O2 sensor, air filter and it is still overheating. I took the car to a computer diagnostic shop and the mechanic can't find any problem. All the water boils out of the radiator into the small reserve tank after I turn the engine off. Please help as my dealer can't find any problems and I have run out of money replacing parts.

Answer:   Check the operation of your main radiator cooling fans. If these fans fail the car's self diagnostic program can not see the problem. Replace the radiator cooling fans to repair as needed, recheck system.

Question: 2003 Pontiac Grand Am Quad 4, miles: 56,000 Recently replaced a cracked cylinder head. All temperature and fan functions were normal. Now I have an abnormal temperature indication (220 degrees) at idle which returns to normal at road speeds at about 2000 RPM. A dealership coolant change used only one gallon (orange coolant) without flushing. Some time after the coolant change, I drove in a 107 degree heat wave. The engine temperature went up to 240 degrees but never did go into the danger or "red zone". I now suspect a problem with the water pump. No coolant loss observed and the weep hole looks OK. Could the impeller be spinning loose or corroded away making it ineffective? To date I have over $3000.00 in repair costs and I'm looking at another $500 if the pump is replaced. The vehicle was an absolute GEM prior to this problem and I wish GM still made them!

Answer: Check for a partially plugged radiator. When the engine overheated sludge or debris may have been dislodged and plugged the radiator. Replace the radiator with new to repair problem.

Question: 2001 Dodge Neon mileage: 66,211. My wife was driving down the freeway at 55-60 mph, the car started heating up on the gauge. She pulled it over, and called me. Upon inspection - both belts are on, all inside fuses are good; all under hood fuses are good. She had the a/c on while on the freeway. After letting it set for 4 hours, I pulled the radiator cap - it was full of water w/coolant, oil level was good, so was the trans fluid level. There were no leaks, either now, or before, the car does not use/leak oil, it's never overheated before, uses no fluids at all. However, after letting it set for the 3 hours, she started it and the temporary gauge didn't move past the 1/3 line, as it always ran that way before. She drove it 11 miles towards home, and the gauge did not go past the normal level, when we stopped at the stoplight near our home, I told her to put on the a/c and watch the temp gauge, we only had to drive 4 miles home, but by the time we got there the gauge was nearing the high heat line. After sitting still in the driveway, running with the a/c running, the car started going hot again. The car has 2 electric fans, however I did not see-hear them run, or turn on at all, is there a fuse that works them? I did not find any such fuse, and I took each one out, both inside the car and inside the engine compartment - and upon inspection - all were good. What should I be looking for; why when the engine is obviously overheating - do the electric fans not come on? What should I do, as we live in rural Arizona and it's dead of summer, the first time it was daylight at 104 degrees, driving home it was 88 degrees, why is it getting hot?

Answer: Yes, there is a fuse that controls the fans. There is also a power relay in the circuit. Check the cooling fans themselves by jumping the circuit with 12-volts to see if they operate. If not replace with new to repair problem.

Question: 2003 Honda Civic SI hatchback mileage: 66,000. Some time ago, I noticed that our Civic was running hot (not overheating yet) and the electric fan didn't turn on. Recently I replaced the thermostat, radiator cap, radiator fan thermo switch but the fan still wouldn't turn on. I know it works because shorting the thermo switch wires turns it on. It normally runs with the temperature parked around center of   the scale but in slow traffic will rise to 3/4 scale. Should the fan turn on then? My Haynes manual doesn't show full electrical diagram and I am not sure if only the thermo switch turns the fan on. Some models had relay also.

Answer:   You may have a faulty thermo-switch. In addition, if you have a blown head-gasket it would allow exhaust to get into the cooling system, which in turn would fool the thermo-switch.

Question:  2002 Mazda B3000 mileage: What causes backpressure in a radiator? I've replaced the water pump, thermostat, radiator, hoses, expansion tank and clutch fan, changed antifreeze etc. The truck still overheats no matter what I've fixed. What am I missing or not seeing?

Answer:  Radiator "backpressure" is caused by a blown head gasket. Replace head gasket with new to repair the problem.

Question: 2002 Honda Accord mileage: 66,000. The electric cooling fan will not turn on. I have replaced the relay. I also can hardwire the fan and it works fine. The car will overheat in a period of time. I thought maybe it was the Engine Coolant Temperature Sensor, but since the dummy engine temperature light came on when it overheated, I suspected that sensor is working fine. I don't know where else to look. Could it be the engine coolant temperature sensor? There are two sensors on the right side of the engine one above the other, which one is the ECT sensor? Even though it warns you of high temperature could it still be bad and not signaling the fan to come on. The AC doesn't work, but should the fan come on anyway when you turn the controls to AC? It doesn't. Do you know where I can get a wiring diagram of the car?

Answer: Try replacing the coolant temperature sensors and the fan control relay with new. Reassemble to recheck system.

Question: 2002 Cadillac Fleetwood mileage: 75,000. Hello, I'm getting two stories from two separate mechanics and need some help here. While driving down the freeway at 60 mph, the dash coolant temp fanlight came on and we pulled over...lots of steam--overheating major. (I had the thermostat changed and radiator flushed 30,000 miles ago) Rolled into the gas station/shop and they said it was a cracked radiator and needed replacement. They are plastic in the Cadillacs. Next day, they called and said there were emissions coming from the radiator, as high as if it were coming from the tailpipe. They suspected a cracked block or blown head gasket and to tow it to my regular mechanic--it runs, but will heat up. My mechanic says they put water in it and drove it, it ran smooth, and they ran a pressure test and it was fine. No water in the oil (didn't mention oil in the water), and they believe its just the radiator that needs replacing, it was normal to have some exhaust coming through the radiator. In addition, I thought I noticed a little white smoke from the tailpipe when they started up the car, which dissipated in a few seconds. And, over the last month, it sounds as if there is "gurgling" going on in the dash, like water going through hoses for the heater. That sound usually happens when I start the car up in the morning, and it has warmed up for a few minutes and I am driving away. What happened?

Answer:   It sounds like you have a radiator that failed causing the engine to overheat and blown the head gaskets. This is a common problem with cars today, the radiator tanks are made of plastic so when they fail it causes other problems. Today's automobile should replace the radiator every 4 years to help stop catastrophic engine failure. eAutoPartStore.com has replacement radiators for about $68.00

Question: 2002 Toyota Camry mileage: 75,000. My radiator was corroded and leaking. A new radiator has been fitted. I have now been told that the head gasket needs to be replaced because there is a major oil leak. This did not exist when I took it into the garage. Is this something that can happen when a new radiator has been fitted? I am now expected to pay a much higher repair bill. Is it likely that the garage could be negligent?

Answer:   It sounds like you have a radiator that failed causing the engine to overheat and blow the head gaskets. This is a common problem with cars today, the radiator tanks are made of plastic so when they fail it causes other problems. Today's automobile should replace the radiator every 4 years to help stop catastrophic engine failure. eAutoPartStore.com has replacement radiators for about $68.00

Question: 1966 Ford Mustang 289 mileage: 221,000. I was replacing the thermostat and put it back together with the housing and intake cleaned free of left over gasket with a air-powered tool and material to clean metal, put on the new gasket with The Right Stuff sealer and new thermostat, started to fill with water and it started leaking out of the passenger side of the housing. I took the housing off again, cleaned everything again, got a new gasket put everything back on and it leaked again. Took everything off again, cleaned it again, tried to make sure the metal was smooth on the housing and the intake, put it back together with the second gasket and more sealer, waited a few hours then filled with water and it leaked again from the same side. What to do now?

Answer:   First thing to do is to make sure the thermostat housing gasket surface is flat. In addition, the mating surface on the intake manifold should be checked for flatness. If both parts check okay, glue the thermostat in place to prevent it from slipping down as you attempt to reassemble the thermostat housing.

Question: 1997 Subaru Forester mileage: 46,000. My Subaru was overheating and lost power. I replaced the spark plugs, coils, thermostat, and fuel filter. This didn't help. I took it to a mechanic and told him the repairs I had done on my own. The next day he said he replaced the thermostat and said it was fixed. I got 4 miles from the shop and it started to overheat so I took it back. After about a week he said it was fixed. He flushed the radiator, changed the water pump, spark plugs, fuel filter, and timing belt. He said the plugs were corroded and the fuel filter was clogged even though I just replaced them. I got in it to leave and it wouldn't start (I have never had a problem with it starting). He said he worked on it outside his shop and it rained so he replaced the air filter because it got wet. Picked it up the next day and drove it about 1 week. During this time, it stayed on the verge of overheating until it overheated again. This time he said it was a water bypass hose. Drove it about 4 miles and it over heated again - told him to keep it until it was fixed. After almost 2 weeks, I went to him and he said he inspected the water pump and timing belt and couldn't find anything wrong. He said it must be a blown head gasket. I had already spent over $800 on repairs and now he wanted at least $1400 more for the head gasket. I asked him if there was anyway to be sure it was the head gasket before he did it and he said there was no way without taking the head off. I told him I wanted my money back and I would take it somewhere else since he hasn't done any repairs that fixed the problem. He wouldn't give me my money back and said that I didn't understand the method of auto repair. He said you start with the least expensive thing that could be wrong and work your way up to the most expensive until it is repaired. I started questioning his ethics as a mechanic. My question mostly is was there a way for him to check for a blown head gasket when I first took it to him?

Answer: Yes, some head gasket problems are hard to detect honestly fooling some mechanics. But this guy should have caught this one by now... rrrrr. Take your car to a top quality repair garage for repair.

Question: 1999 Mercedes CLK 320 Coupe mileage: 84,000. I would appreciate any help you may suggest for a problem I have with my faithful Mercedes. Now with 84,000 miles and almost perfect bodywork, please tell me I don't have to change it! It started overheating and the garage local to my workplace (non Mercedes) identified that the fan was not working. A new fan however did not stop the overheating. A chemical test on the coolant identified that the head gasket was blowing. Subsequent strip down confirmed this as being on the 5th and 6th pots. After pressure testing, skimming and refitting the head, as well as changing out the thermostat, sender and a few other components, I still was left overheating. The radiator was then removed for testing, and re-coring carried out. The car now goes brilliantly, normally runs about 80 deg C, but still tends to overheat whenever I get in a traffic jam, and sometimes at other odd occasions. It hasn't actually boiled over, but the temperature gauge seems to fluctuate pretty wildly at times, sometimes going over 250 degree F before dipping back down again. I have checked that the fan is working even when the temperature gauge is showing hot. Any suggestions - I am getting desperate! I am bit of a mechanic myself so if I can repair it let me know.

Answer: It sounds like you have a partially plugged radiator, replace with new to repair the problem. As far as changing it yourself it is about a hour and 1/2 job. Replace to refill and recheck system. And as far as how tough the job is, its like my Dad always said (Bob) "it's just nut's and bolt's... not to bad."

Question: 2002 Mercedes Benz ML500 mileage: 81,000. My question is my runs extremely hot when idling for a couple of minutes. It could be 30 below zero and if I stop moving for a couple of minutes, my temperature goes to red line. Yet, it has never boiled over. This is what I've done so far to try to fix the problem: Replaced the radiator, thermostat, checked the gauges, and got the heads done along with a valve job. I pretty much replaced the whole cooling system, yet it still over heats. The only way I can get the temperature down at that point is either start driving, which I can't always do, or rev the engine a little and within seconds, the temperature drops. The car drives great and I have no problems with the car rather than the heat. I do not want to burn out the engine plan on having the car for at least another 100,000. Any ideas?

Answer:   Your fan clutch maybe failing and needs to be replaced. Replace with new unit to recheck system.

Question: 2002 Toyota Camry mileage: 51,091. My condenser-cooling fan and engine-cooling fan both stop working at the same time. When I turn the air conditioner on the fans, they do not come on. I check all my fuses and relays and they seem to be all right. What else could cause both fans not to work because the engine-cooling fan will not come on to keep the engine temperature stable?

Answer:   It sounds like your radiator cooling fans need replacing. Replace to recheck system.

Question:   2001 Dodge Ram 1500 mileage: 70,000. My wife's truck is overheating and losing coolant. However, there is no water in the oil and no oil in the coolant. I continue to add coolant, as it gets low. What could be the problem?

Answer:   Overheating is usually caused by a partially plugged radiator. In addition, pressure check the cooling system for any leaks. Replace radiator with new.

Question:  2003 Acura CL 3.2 mileage: 67,700. Noted for several months coolant temperature rising but never very high. Opened hood to change oil and noted no coolant in overflow tank. Fluid level in radiator low as well. After refill, fluid noted to be seeping out around seal between upper plastic part and metal body. Replaced with new radiator from eAutoPartStore.com. After refilling and bleeding out air, noted fan wouldn't come on even when temp approaching straight up on gauge but would come on normally with a/c or if ECT switch shorted across. Replaced ECT switch but no change. Tested ECT switch that was pulled (after the fact!) and it worked normally. Tried running it and burping it to get any air away from the ECT switch but no change. Even tested the relay in the under the hood box. It works normally with and without power. Where to go from here?

Answer:   The radiator fan may be functioning properly. Replace radiator fan assembly with new to repair problem.

Question:   2004 Ford Escape mileage: 55,0000. Need to fix car for family ASAP. Once car is driven for a short while, we recognize a strong anti-freeze smell in the car, then the temperature gauge begins to rise to hot, and smoke comes in through the windshield vents and heater vents to the inside of the car, steaming up the windows and causing the engine to become extremely hot. When explaining this problem over the phone to the Ford dealership, they, without seeing the car, identified the situation as appearing to be a heater core problem. I looked on our contract for extra insurance coverage for major problems with our car, and, of course, the heater core is not covered. Asking the cost to fix, they explained approximately $500.00+. Because of medical issues, we do not have the cash to pay a dealership or otherwise at this time. Could you share with me if in fact it is a heater core issue; could it be anything else; and, could I fix this myself, as I have replaced a heater core on one of my vehicles several years ago. I understand that it is more difficult to work on the newer cars these days, which almost forces us to take it in. But, in this case, if you do not think it possible to fix on our own, are there hoses, or something we could detach to avoid the overheating, until we have additional funds to pay for this job (even if, in fact, we do not have heat - since it is summertime - that would not be a problem). Also, is there somewhere on the web that would give us step-by-step instructions on how to fix such things (and maybe even pictures, as to where to find these items on the car) on our own for, in this case, a Ford Escort Wagon (1997). Thank you for your advice at your earliest convenience. (Currently, we can drive off our hill, but even to get back home from the local grocery store, going up hill, the car begins to heat, etc.)

Answer:   It definitely sounds like the heater core is leaking. There is a temporary fix that is relatively easy to perform. There are two heater hoses, one in and one out to the heater core. We would recommend, "looping" the two heater hoses taking the heater core out of the system. Do not plug the hoses.

MORE: Car over heating questions

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